#include <bits/stdc++.h>
using namespace std;
#define int long long
const int INF = 3e13;
void transform(int &x, int &y) {
	x -= y;
	y = (y << 1) + x;
}
int floorDiv(int a, int b) {
	return (a/b) - ((a^b)<0 && (a%b));
}
pair<int,int> xRange(int vx, int dx, int a, int k) {
	int lft = 0, rgt = INF;
	if(vx+k>0) lft=max(lft,floorDiv(dx-a+vx+k-1,vx+k));
	else if(vx+k<0) rgt=min(rgt,floorDiv(dx-a,vx+k));
	else if(dx>a) rgt=-1;
	if(vx-k>0) rgt=min(rgt,floorDiv(dx+a,vx-k));
	else if(vx-k<0) lft=max(lft,floorDiv(dx+a+vx-k+1,vx-k));
	else if(dx+a<0) rgt=-1;
	return {lft,rgt};
}
int test(int vx, int vy, int dx, int dy, int a, int k) {
	auto [lx, rx] = xRange(vx,dx,a,k);
	auto [ly, ry] = xRange(vy,dy,a,k);
	int fst = max(lx,ly);
	if(fst<=rx&&fst<=ry) return fst;
	else return INF;
}
int test2(int vx, int vy, int dx, int dy) {
    if(dx&&!vx) return INF;
    if(dy&&!vy) return INF;
    if(!dx && !dy) return 0;
    if(!vx) return (dy%vy?INF:(((dy^vy)<0)?INF:dy/vy));
    if(!vy) return (dx%vx?INF:(((dx^vx)<0)?INF:dx/vx));
    if(dx*vy==dy*vx) return (dx%vx?INF:(((dx^vx)<0)?INF:dx/vx));
    return INF;
}
int solve() {
	int n, k, x, y; cin >> n >> k >> x >> y;
	transform(x,y);
	int xx[n], yy[n], sx = 0, sy = 0;
	for(int i=0;i<n;i++) {
		cin>>xx[i]>>yy[i];
		transform(xx[i],yy[i]);
		sx += xx[i];
		sy += yy[i];
	}
	if(!x&&!y) return 0;
	int ans = INF;
	for(int cx=0,cy=0,i=0;i<n;i++) {
		cx += xx[i];
		cy += yy[i];
		ans=min(ans,test2(sx,sy,x-cx,y-cy)*n+i+1);
	}
	return (ans==INF?-1:ans);
}
main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	int T; cin >> T;
	while(T--) cout<<solve()<<"\n";
}